The B-11 NMR spectra of xRb(2)S + (1 - x)B2S3 glasses in the range 0 less t
han or equal to x less than or equal to 0.75 and of xCs(2)S + (1 - x)B2S3 g
lasses in the range 0 less than or equal to x less than or equal to 0.60 ar
e reported. The addition of Rb2S to B2S3 creates on average approximately t
wo and one-half tetrahedral borons for each added sulfur ion, whereas It is
found that the addition of Cs2S creates approximately 2 tetrahedral borons
for each added sulfur ion. This behavior while more similar to that seen i
n the alkali berate glasses, contrasts that seen in the Na and K thioborate
glasses, where six to eight and three, respectively, tetrahedral borons ar
e formed for every sulfide anion added to the glass. These findings are sup
ported by the IR and B-11 NMR spectra of the di-thioborate polycrystals (c-
Rb2S:2B(2)S(3) and c-Cs2S:2B(2)S(3)) whose structures appear to be comprise
d of two BS4 tetrahedrals and two BS3 trigonals (N-4 similar to 0.5) like t
hat in the alkali di-borate phases for both Rb and Cs. Unlike the B-11 NMR
resonances of the sodium thioborate glasses where a single sharp line is ob
served for the tetrahedral boron site and a single quadrupolar broadened li
ne is observed for all the trigonal sites, a third resonance line is observ
ed at high alkali fractions for the rubidium and cesium thioborate glasses.
This new structural feature may arise from asymmetric MBS2 (meta-thioborat
e groups) or tetrahedral boron groups possessing a non-bridging sulfur. (C)
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